60
Journal of Medicinal Chemistry, 1971, Vol. 14, S o . 1
NOTES
mice and a relatively small quantity of drug. The mice are pretreated with the test compounds at :L set, \--Y 1-1 period before induction of arrhythmias with CI-1Cl3. During this period symptoms of acute toxicity (ataxia, Antimicrobial Activity.-The compound' listed iii coIivuIsions, etc.) can be noted. The mouse is then Table I w r e tested in vitro against Esc/ie,,zciiz'a c( l i , subjected t o ;I CHC13 atmosphere until respiration Bacillus a?ifh,acis, and Staphylococcus aul.eii.9, u'itig ;1 ceases. This procedure induce.; a high incidence of tube dilution method and the disk diffusion ventricular fibrillation in the animals. In the exl-,osetl Of all the compounds tested, ;Ir-I.i-trifluorometli\ 1-1% 3 + - hearts the fibrillatory niovenientc: can he observed and 4-thiadiazol-2-glIcarbamic acid +but\ 1 eyter (22) :it the cardiac rate counted. Thc protection afforded hy 200 ~ g ' minhibited l the gronth of B. authmcis, aftcr 24 pretreatment with an antiarrhythmic compound c:~n hr incubation at 37'. ,411 other compounds *]io\\ ed then he determined. only slight antimicrobial activit) probably due to lo\\ solubility and 'or poor diffusion. Results and Discussion Experimental Section4 [ 5-Trifluoromethyl-l,3,4-thiadiazol-2-yl] carbamic Acid n-Butyl Ester ( 22).-2-ilmino-5-trifluorome~hyl-l,3,4-thiadiazole2 (1.67 g, 0.01 mole) iri 15 ml of dry CIIC13, was refluxed for 3 h r with 1.64 g (0.012 mole) of n-butyl chloroformate. Removiiig
the solvent followed by crystii of the residue from gave 2.42 g (90yo,)of 22, whit,e cryxtala, m p I S " . compds listed iri Table I were prepared similarly.
aq EtOH, The other
X-1[ethyl-A: - phenylethyl- 1,2,3,4-tetrahydro- 6 - mehydrochloride (1) had previously been shown to possess potent myocardial depressant activity.* Because of its past indications of antiarrhj thmic activity and because of its availability 1 !vas investigated in detail. The results are shown in Table I. The procedure used to induce
t hoxy-4,4-dimet hyl-2-napht hylamine
Acknowledgments-The authors gratefully acknowledge the constant encouragement of Dr. A. Alikhani of Tehran University.
'r.iHLI.:
I J I ~ F O N i ;.\SI>.\FTb:K TRI:.iTMI:ZT
Dose (3) C. IT. Collins, "Microbiological Methods," J3uthernorths, London (1964). (4) hlelting points were taken on a Bofler hot stage microscope and \\-ere uncorrected. T h e ir spectra were determined n4th a Leitz Model 111 spectrograph. X m r spectra were obtained on a Varian A60.4 instrument.
(mg/kg)
40 40
0.3 3 0
m -
i(l
:12.5 3;1.0 72.3 02.3 100.0
i
.)
125 150 175
D. h1. G R A E F F W. , ~ ~E. JOHNSIX,* A. 11. h I A K l I X
c. 1>. St. DENiYIS, . i K D
College of Pharmacy, Washington State L'niverszty, Pullman, Washington 99163
Xumbrr % of mice protected
COllt lols , 0i
100
A New Series of Antiarrhythmic Agents. The 2-Aminotetralinsl"
I
~ H L O H o F ( ~ l t h f - I s D ~ c lCl.D iliDI.iC .~KHHTT€IMI.\S
40 40 40 40
WITH 1
.\yerage rate (heats/min =tS.E.)
C' I C
".I
toxic
fatal
3 3 1 . 9 1 i 16.61
0.0
0.0 0.0
289 62 i 10.6:3 0.0 0.0 228.00 i- 14.83 166.08L13.19 0.0 146.88 i- 13.04 14.0 136.00 + 7.74 47.*i 124.24 sfr 6.75 69.4
0.0 0 0 0 0 0.0
7
cj
arrhythmias in vivo resulted in the production of arrhythmia and fibrillation in 100% of the nontreated control animals. The ED,, of 1 was 94.41 mg/kg CH
CH O ~ C H & H ,I 4 H , * H C l
Received -Way 16, 1970
The synthesis arid analgetic properties of some substituted 2-aminotetralins were previously reported by Martin, et al. Subsequent pharmacological investigations have shown these compounds to possess marked negative chronotropic and mild negative inotropic activities in spontaneously beating guinea pig atria.3 I n order to determine the relationship between the toxicity and the antifibrillatory activity of the series of 2-aminotetralins in vivo a screening method developed by Lawson4 was used. This procedure enables rapid screening of the compounds with a large number of *
To whom correspon,dence concerning this research should be addressed. (1) (a) This research was supported in part by a Washington State Heart Association Grant No. 6970-6. (b) National Science Foundation Fellow, 1969-1970. (2) A . R . Martin, A. P. Parulkar, I).J. Gusseck, L. J. Anderson, G . L . Grunewald, and .4.I. White, J. P h a r m . Sci.. 68, 340 (1969). (b) 1'. S. P a i , A . P. Parulkar, A . R . illartin, and A . I. White, i b i d . , in press. (3) \V. E. Johnson, D. hl. Graeff, A . R . Martin, and A . I. White, Life Sei., 9 , 471 (1970). (4) J. W.Lawson, J . Pharrnacol. E x p . Ther., 160, 22 (1968).
CH, CH 1
(0.262 mmole/kg). The average heart rate corresponding to this dose was graphically estimated to be 160 beats/min. KO toxicity was noted at this ED60 dose. Compound 1 showed a good degree of antiarrhythmic activity in relation to its toxicity. Only at the higher doses, approaching 100% protection, does significant toxicity result, generally manifested as mild ataxia. Convulsions and death occurred only at the highest dose studied. This compound was used as a standard for comparison of all the other analogs tested. The doses used for the other compounds were the equimolar equivalents of the ED,, dose for 1 (0.262 mmole/ kg). The results are shown in Table 11. The analogs 2-5 have chemical structures most closely resembling 1. These compounds involve only substitutional changes on r\' atom. They varied greatly in activity ranging from 0 t o 100% protection from fibrillation. The
NOTEB
Journal of Medicinal Chemistry, 1971, Vol. 14, No. 1 61
toxicity also varied greatly. I n general, the most active analogs were the most toxic. The externally observable 6 ? ~ 0m r0- & 0 0 36 0 0 0 0 0 0g~60 ~ toxic responses in mice to the 2-aminotetralins appeared similar t o amphetamine toxicity. The animals first exhibited nervousness that was followed by skeletal muscle tremors. I n the cases of more acute toxic responses, the tremors progressed to frank convulsions with loss of coordinated respiration and often death. Loss of equilibrium or ataxia typically preceded the convulsive state. Compound 2 showed no activity or toxicity, whereas 3 and 4 resulted in significant toxicity in the doses used. Compound 5 showed 20% protection with the lack of any observed toxicity. Compounds 6 and 7 possess substitutions on N and the substitution of P h for a Me at the 4 position on the saturated ring. Both of these compounds exhibited favorable protection. Compound 6 appeared somewhat less effective than 1 in producing antifibrillatory protection, 46.7% compared with 5Oy0 for 1, and lacks toxicity at this dose. Compound 7 gives better antifibrillatory protection, 66.7%, but ataxia and mild convulsions resulted in 83,3y0of the animals. Compounds 8 and 9 have substitutions on both the N and the aromatic portion of the ring system. These compounds exhibited very little antiarrhythmic efficacy. Compound 8 exhibited very high toxicity resulting in death in 100% of the animals. Compounds 9 and 10 both showed very low antifibrillatory effect. Compounds 11-14 differ from 8 and 9 by the introduction of Me at C-2. All of these compounds show antiarrhythmic activity. I n fact, 11, 12, and 13 exhibited considerable toxicity. Compound 11 showed good protection but no toxicity. Compounds 15-17 lack substitution on the aromatic ring but possess a benzyl group at C-2. The protection provided by these agents ranged from 10 to 84.21y0. All of these compounds possessed a high degree of toxicity. Compounds 15 and 16 may show some antiarrhythmic effectiveness at lower doses, however the unfavorable toxicity :protection ratio for 17 and 18 would appear to eliminate them as possible antiarrhythmic agents. Four standard antiarrhythmic agents (quinidine, dlpropranolol, procainamide, and lidocaine) were included in the study for comparative purposes. The results are shown in Table 111. The results obtained for the standard antiarrhythmic agents compare favorably with those reported by L a ~ s o n . The ~ ED50dose reported for quinidineaS04 was 72 mg/kg, dl-propranolol.HC1, 35 mg/kg, and procainamide.HC1, 102 mg/kg. The dose which was used was equimolar to the EDs0dose for 1. This dose gave the following results: quinidine.SO4, 118 mg/kg, gave 83.33% protection, dl-propranolol. HC1,77 mg/kg, gave 60.00~0,and procainamide.HC1, 59 mg/kg, gave 13.3370 protection. The toxicity varied greatly with quinidine and procainamide being nontoxic in the dose used but lidocaine showed toxicity in 86.770 of the animals and dl-propranolol in 46.7%. None of the 4 compounds caused fatalities to occur. Although the limited number of 2-aminotetralins available restricts the development of any thorough structure-activity theory for antifibrillatory activity at this time, some important observations may be made which should aid in the development of additional analogs with antiarrhythmic activity. Consideration of , 0 0 m 0 0 0 0 0 0 0 0 0 m 0 m r - 0
I
L
Y
62 Journal of Medicinal Chemistry, 1971, Vol. 14, N o . 1
Drug
Quinidine. SO, dl-Propranolol .HCl Procainamide HC1 Lidocaine. HC1
Number of mice
Equimolar dose ( m r / k d
40
118 47 77 47 ,;is 92 70 .iX
40
40 40
structural requirements for substitution on N is unclear since good protection resulted from compounds having primary, secondary, and tertiary amine groups. I n almost all cases, the primary amine derivatives caused greatly reduced toxicity when compared with the analogous substituted compounds (see 5, 6, 11, 14). I n the comparison of the secondary amine analogs, an increase in the lipid solubility or hydrophobic character of the substituent increased both the antifibrillatory protection and the toxicity (see 3, 4). The substitution of more hydrophobic groups at any position on the saturated ring increased the antifibrillatory activity and also the toxicity (see 6, 7, and 9-17). This may be due to an enhanced transport capability related to the relative partition characteristics of the molecule, as described by Levy,5 rather than any specific receptor requirement. From the results it is apparent that some of the 2aminotetralins tested possess very good antifibrillatory protection properties compared with the commonly used antiarrhythmic agents and show little or no acute toxicitjr in effective doses. The relationship between toxicity and antiarrhythmic efficacy is very important. Although many agents possessing relatively potent antiarrhythmic activity have been developed, a great number of them have exhibited untoward toxic properties. Thus the absence of noticeable toxicity in dosage levels resulting in good antiarrhythmic activit > in the screening experiments in highly desirable.6 Experimental Section Adult male mice (Carworth strain CF 1) (22-28 g were weighed and injected ip with the test compound and placed in separate glass containers. The injections were given to groups of animals with 2-min intervals between individual animal treatments. After injection each animal was observed for toxic symptoms. Exactly 10 min after treatment each animal wab transferred to a 250-ml beaker that held a cotton pad saturated with 20 ml of CHCla. The animal was removed immediately after respiratory arrest and the heart was quickly exposed by removing the anterior thoracic wall without touching the heart with the surgical instruments. The heart rate and fibrillatory movements were recorded with the aid of a stop watch and a binocular dissecting microscope. Any animal showing fibrillation or ventricular rates in excess of 200 beats/min was defined as unprotected. All animals exhibiting rates below 200 beats/min were reported as protected from fibrillation. In all cases where sufficient drug was available groups of 40 mice were used. Values for the percentage of animals protected were used to calculate an EDSOaccording to Litchfield and W i l c ~ x o n . ~All other statistical calculations were performed according to Steel and Torrie? (5) J. V. Levy, Eur. J. Pharmacol., 2, 250 (1968). (6) M. M . Winbury, A n n . N . Y . Acud. Sci., 64, 564 (1956). (7) J. T. Liichfield, J r and F. Wilcoxon, J . Pharmacol. E z p . Ther., 96, 99 (1949).
(8) R. G . D. Steel and J. H. “Torrie, Principles and Procedures of Siaiistica,” McGraw-Hill, New York, N. Y., 1960.
Average r a t e :beats/min =k S.E.)
1 2 9 . 0 3 j, 1:;,42 18.i . G I =k 12 .‘G 291,.57 i. 17.11 18’2 77 i 14.78
:6
,.o.’
protected
toxic
fatal
8 : : .:i 60. 0 I :3 , 3 ;i6. 7
0.0 16.0 0.0 86.7
0 0 0 0
0
0 0 0 0
Antimalarial and Other Biological Activities of Some Y-Alkyl and 2’-Aryl Derivatives of Cinchona Alkaloids’ J. P. YARDLFX,lt. E. BRIGHT,LEO LINE, 13. W. A . I t ~ e s P. , B. KussmL, A N D HERCHEL SMITH
Research Division, W y c t h Laboratories, Inc., Radnor, Pennsylvania, and ‘$1alariu Screening Luhoratory, 17nincrsit?/of Xiami, hfianii, Florida
R ~ ~ i v June t d 1 7 , 1570
lye report ail investigation undertaken primarily to compare with activities of 2’-alkyl and 2’-aryl derivatives of quinine, quinidine, and their 10,ll-dihydrides against experimental malarias caused by Plasnzodium b u g h e z and P . ljallinaceum in mice and chicks, respectively, in the Eramen-orli of studying the effect of blocking the 2 position of the quinoline ~ i u c l e u s . ~ -The ~ substances were also examined for cardiac antiarrythmic and antibacterial activity. The 2’-alli>1 and 2’-ar>1 derivatives were prepnred from the alliuloid ar-S-oxides and appropriate Grignard or Li organometallic reagents (cf. ref 5 ) . Satisfactory yields were obtained with simple primary alkyl Grignard reagents f-RuhIgBr and sec-RAIgBr yielded predominantly the parent diamine along with a lou yield of the corresponding 2’-allq 1 derivative. The re:tction failed with t-BuJIgBr. Hou ever, 2’-t-Bu and 2’-cyclopropylquinidine ivere obt :lined from quinidine x - X oxide and the corresponding Li alkyl. The 10,lldihydroquinidines mid dihydroquinirles \\ere obtained by catalytic hydrogenation of the appropriate quinidine and quinine derivative I and 11, respectively. Under the conditions used, no 1osb of halogen from the 2’-llnlophenyl derivatives wai: observed. Physical coiist ants for the nexv compounds :tiid other data w e listed in Tables I-IV. Antimalarial Activity.-Activity n as measured against P.berqhei in mice and P . yallinaceuni i n chicks by previouqly described methods.6 The data in Table I shou that 2’-alkyl subqtituents lo\\ er the maximum tolerated dose (JITD) thereby restricting testing t o lo\\ dosage levels. hlso, ?’-aryl substituents confer 111(1) This paper is Contribution No. 688 from t h e Army Research Program o n Malaria. ( 2 ) hI. M. Rapport, 1. E. Senear, J . F. Mead, and J. B.Koepfli, J . A m e r . Chem. Soc., 68, 2697 (1946). (3) F. E . Kelsey, E. M . K , Geiling. F. I
